PRODUCTS

HEMA (HYDROXYETHYL METACRYLATE)

CAS No. : 868-77-9

Hydroxyethylmethacrylate or HEMA (Hydroxyethyl Metacrylate) is the organic compound with the formula H2C=C(CH3)CO2CH2CH2OH. It is a colorless viscous liquid that readily polymerizes. HEMA (Hydroxyethyl Metacrylate) is a monomer that is used to make various polymers.

CAS No. : 868-77-9
EC No. : 212-782-2

Synonyms:
2-HYDROXYETHYL METHACRYLATE; 868-77-9; Glycol methacrylate; Hydroxyethyl methacrylate; Glycol monomethacrylate; Ethylene glycol methacrylate; HEMA; 2-(Methacryloyloxy)ethanol; 2-Hydroxyethylmethacrylate; Mhoromer; Ethylene glycol monomethacrylate; Monomer MG-1; 2-hydroxyethyl 2-methylprop-2-enoate; Methacrylic acid, 2-hydroxyethyl ester; (hydroxyethyl)methacrylate; HYDROXYETHYL METACRYLATE; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester; PHEMA; beta-Hydroxyethyl methacrylate; NSC 24180; 2-Hydroxyethyl 2-methylacrylate; UNII-6E1I4IV47V; PEG-5 methacrylate; CCRIS 6879; CHEBI:34288; Ethylene glycol, monomethacrylate; HSDB 5442; PEG-MA; POLYHYDROXYETHYL METHACRYLATE; EINECS 212-782-2; BRN 1071583; Monomethacrylic ether of ethylene glycol; 6E1I4IV47V; polyethylene glycol methacrylate; .beta.-Hydroxyethyl methacrylate; 1,2-Ethanediol mono(2-methyl)-2-propenoate; MFCD00002863; 12676-48-1; methacryloyloxyethyl alcohol; Poly-hema; Bisomer HEMA; 2-Hydroxyethyl methacrylate, 97%, stabilized; Hydroxymethacrylate gel; Polyglycol methacrylate; Glycol methacrylate gel; Poly(hydroxyethyl methacrylate); PEG-8 methacrylate; hydroxyethylmethacrylate; hydroxyehtyl methacrylate; hydroxylethyl methacrylate; 2-hydroxyetyl methacrylate; DSSTox_CID_2128; Epitope ID:117123; UNII-9XEM35MI4M; EC 212-782-2; 2-hydroxylethyl methacrylate; 2-hydroxy ethyl methacrylate; 2-hydroxyethyl(methacrylate); 9XEM35MI4M; DSSTox_RID_76499; UNII-W321DU8DF9; DSSTox_GSID_22128; SCHEMBL14886; WLN: Q2OVY1&U1; 2-methacryloyloxyethyl alcohol; 25249-16-5; 4-02-00-01530 (Beilstein Handbook Reference); ethyleneglycol monomethacrylate; KSC176I7D; BIDD:ER0648; Methacrylic acid 2-hydroxyethyl; W321DU8DF9; CHEMBL1730239; DTXSID7022128; CHEBI:53709; CTK0H6471; poly(ethylene glycol methacrylate); poly(ethylene glycol) methacrylate; 2-Hydroxyethyl methacrylate, 98%; HYDROXYETHYL METACRYLATE; 2-Hydroxyethyl 2-methylacrylate #; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, homopolymer; HYDROXYETHYL METACRYLATE; KS-00000X9T; NSC24180; ZINC1608929; 2-Hydroxyethyl methacrylate (HEMA); Tox21_200415; ANW-38400; NSC-24180; poly(ethylene glycol monomethacrylate); AKOS015899920; Methacrylic Acid 2-Hydroxyethyl Ester; CS-W013439; DS-9647; NE10234; NCGC00166101-01; NCGC00166101-02; NCGC00257969-01; AK159194; CAS-868-77-9; K551; LS-89930; 2-Hydroxyethyl methacrylate,ophthalmic grade; 1,2-Ethanediol, mono(2-methyl)-2-propenyl; FT-0628271; M0085; NS00008941; 5627-EP2269995A1; 5627-EP2275418A1; C14530; Methacrylic acid, polyethylene glycol monoester; 2-Methyl-2-propenoic acid, 2-hydroxyethyl ester; alpha-methacryloyl-omega-hydroxypoly(oxyethylene); Q424799; J-509674; 2-Hydroxyethyl methacrylate, embedding medium (for microscopy); Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propen-1-yl)-omega-hydroxy-; Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propenyl)-omega-hydroxy-; 2-Hydroxyethyl methacrylate, >=99%, contains <=50 ppm monomethyl ether hydroquinone as inhibitor; 2-Hydroxyethyl methacrylate, contains <=250 ppm monomethyl ether hydroquinone as inhibitor, 97%; Hema-ema; Hydroxyethyl methacrylate-ethyl methacrylate; 26335-61-5; EMA HEMA; Hydroxyethylmethacrylate-ethylmethacrylate copolymer; HYDROXYETHYL METACRYLATE; SCHEMBL5534844; CTK4F7688; DTXSID70180949; 2-Propenoic acid, 2-methyl-, ethyl ester, polymer with 2-hydroxyethyl 2-methyl-2-propenoate; Hydroxyethylmethacrylate; 2-HYDROXYETHYL METHACRYLATE; hidroksietilmetakrilat; (Hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester; Methacrylic acid, 2-hydroxyethyl ester; β-Hydroxyethyl methacrylate; Ethylene glycol methacrylate; Ethylene glycol monomethacrylate; Glycol methacrylate; Glycol monomethacrylate; Hydroxyethyl methacrylate; Monomer MG-1; 2-(Methacryloyloxy)ethanol; Mhoromer; 2-Methyl-2-propenoic acid, 2-hydroxyethyl ester; Bisomer HEMA; GMA; HEMA; 1,2-Ethanediol, mono(2-methyl)-2-propenyl; NSC 24180; 1,2-Ethanediol, mono(2-methyl)-2-propenoate; 868-77-9; Glycol methacrylate; glikol metakrilat; Hydroxyethyl methacrylate; hidroksimetil metakrilat; Glycol monomethacrylate; glikol monometakrilat; hikroksietil metakrilat; metakrilate; iki hidroksimetil metakrilat; hidroksi etil metakrilat; methakrilat; hidroksi metil metakrilat; Ethylene glycol methacrylate; HEMA; 2-(Methacryloyloxy)ethanol; etilen glikol metrakrilat; akrilat; akrilate; 2-Hydroxyethylmethacrylate; Mhoromer; Ethylene glycol monomethacrylate; Monomer MG-1; 2-hydroxyethyl 2-methylprop-2-enoate; Methacrylic acid, 2-hydroxyethyl ester; hidroksietil ester; hidroksi etil ester; (hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester PHEMA, h e m a; beta-Hydroxyethyl methacrylate; beta hidroksi metakrilat; NSC 24180; 2-Hydroxyethyl 2-methylacrylate; UNII-6E1I4IV47V; PEG-5 methacrylate; CCRIS 6879; CHEBI:34288; Ethylene glycol, monomethacrylate; HSDB 5442; PEG-MA; POLYHYDROXYETHYL METHACRYLATE; EINECS 212-782-2; BRN 1071583; Monomethacrylic ether of ethylene glycol; metakrilik asit; 6E1I4IV47V; polyethylene glycol methacrylate; .beta.-Hydroxyethyl methacrylate; 1,2-Ethanediol mono(2-methyl)-2-propenoate; MFCD00002863; 12676-48-1; methacryloyloxyethyl alcohol; Poly-hema; poli hema; Bisomer HEMA; bizomer hema; 2-Hydroxyethyl methacrylate, 97%, stabilized; Hydroxymethacrylate gel; hidroksi metakrilat jel; Polyglycol methacrylate; Glycol methacrylate gel; HYDROXYETHYL METACRYLATE; Poly(hydroxyethyl methacrylate); PEG-8 methacrylate; hydroxyethylmethacrylate; hydroxyehtyl methacrylate; hydroxylethyl methacrylate; 2-hydroxyetyl methacrylate; DSSTox_CID_2128; Epitope ID:117123; UNII-9XEM35MI4M; EC 212-782-2; 2-hydroxylethyl methacrylate; 2-hydroxy ethyl methacrylate; 2-hydroxyethyl(methacrylate); 9XEM35MI4M; DSSTox_RID_76499; UNII-W321DU8DF9; DSSTox_GSID_22128; SCHEMBL14886; WLN: Q2OVY1&U1; 2-methacryloyloxyethyl alcohol; 25249-16-5; 4-02-00-01530 (Beilstein Handbook Reference); ethyleneglycol monomethacrylate; KSC176I7D; BIDD:ER0648; Methacrylic acid 2-hydroxyethyl; W321DU8DF9; CHEMBL1730239; DTXSID7022128; CHEBI:53709; CTK0H6471; poly(ethylene glycol methacrylate); poly(ethylene glycol) methacrylate; 2-Hydroxyethyl methacrylate, 98%; 2-Hydroxyethyl 2-methylacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, homopolymer; KS-00000X9T; NSC24180; homopolimer; homo polimer; LS-89930; 2-Hydroxyethyl methacrylate,ophthalmic grade; 1,2-Ethanediol, mono(2-methyl)-2-propenyl; 2-Hydroxyethyl methacrylate, embedding medium (for microscopy); Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propen-1-yl)-omega-hydroxy-; Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propenyl)-omega-hydroxy-; 2-Hydroxyethyl methacrylate, >=99%, contains <=50 ppm monomethyl ether hydroquinone as inhibitor; 2-Hydroxyethyl methacrylate, contains <=250 ppm monomethyl ether hydroquinone as inhibitor, 97%; Hydroxyethylmethacrylate; 2-HYDROXYETHYL METHACRYLATE; 868-77-9; Glycol methacrylate; Hydroxyethyl methacrylate; Glycol monomethacrylate; Ethylene glycol methacrylate; HEMA; 2-(Methacryloyloxy)ethanol; 2-Hydroxyethylmethacrylate; Mhoromer; Ethylene glycol monomethacrylate; Monomer MG-1; 2-hydroxyethyl 2-methylprop-2-enoate; Methacrylic acid, 2-hydroxyethyl ester; (hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester; PHEMA; beta-Hydroxyethyl methacrylate; NSC 24180; 2-Hydroxyethyl 2-methylacrylate; UNII-6E1I4IV47V; PEG-5 methacrylate; CCRIS 6879; CHEBI:34288; Ethylene glycol, monomethacrylate; HSDB 5442; PEG-MA; POLYHYDROXYETHYL METHACRYLATE; EINECS 212-782-2; BRN 1071583; Monomethacrylic ether of ethylene glycol; 6E1I4IV47V; polyethylene glycol methacrylate; .beta.-Hydroxyethyl methacrylate; 1,2-Ethanediol mono(2-methyl)-2-propenoate; MFCD00002863; 12676-48-1; methacryloyloxyethyl alcohol; Poly-hema; Bisomer HEMA; 2-Hydroxyethyl methacrylate, 97%, stabilized; Hydroxymethacrylate gel; Polyglycol methacrylate; Glycol methacrylate gel; Poly(hydroxyethyl methacrylate); PEG-8 methacrylate; hydroxyethylmethacrylate; hydroxyehtyl methacrylate; hydroxylethyl methacrylate; HYDROXYETHYL METACRYLATE; 2-hydroxyetyl methacrylate; DSSTox_CID_2128; Epitope ID:117123; UNII-9XEM35MI4M; EC 212-782-2; 2-hydroxylethyl methacrylate; 2-hydroxy ethyl methacrylate; 2-hydroxyethyl(methacrylate); 9XEM35MI4M; DSSTox_RID_76499; UNII-W321DU8DF9; DSSTox_GSID_22128; SCHEMBL14886; WLN: Q2OVY1&U1; 2-methacryloyloxyethyl alcohol; 25249-16-5; 4-02-00-01530 (Beilstein Handbook Reference); ethyleneglycol monomethacrylate; KSC176I7D; BIDD:ER0648; Methacrylic acid 2-hydroxyethyl; W321DU8DF9; CHEMBL1730239; DTXSID7022128; CHEBI:53709; CTK0H6471; poly(ethylene glycol methacrylate); poly(ethylene glycol) methacrylate; 2-Hydroxyethyl methacrylate, 98%; 2-Hydroxyethyl 2-methylacrylate #; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester, homopolymer; KS-00000X9T; NSC24180; ZINC1608929; 2-Hydroxyethyl methacrylate (HEMA); Tox21_200415; ANW-38400; NSC-24180; poly(ethylene glycol monomethacrylate); AKOS015899920; Methacrylic Acid 2-Hydroxyethyl Ester; CS-W013439; DS-9647; NE10234; NCGC00166101-01; NCGC00166101-02; NCGC00257969-01; AK159194; CAS-868-77-9; K551; LS-89930; 2-Hydroxyethyl methacrylate,ophthalmic grade; 1,2-Ethanediol, mono(2-methyl)-2-propenyl; FT-0628271; M0085; NS00008941; 5627-EP2269995A1; 5627-EP2275418A1; C14530; Methacrylic acid, polyethylene glycol monoester; 2-Methyl-2-propenoic acid, 2-hydroxyethyl ester; alpha-methacryloyl-omega-hydroxypoly(oxyethylene); Q424799; J-509674; 2-Hydroxyethyl methacrylate, embedding medium (for microscopy); Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propen-1-yl)-omega-hydroxy-; Poly(oxy-1,2-ethanediyl), alpha-(2-methyl-1-oxo-2-propenyl)-omega-hydroxy-; 2-Hydroxyethyl methacrylate, >=99%, contains <=50 ppm monomethyl ether hydroquinone as inhibitor; 2-Hydroxyethyl methacrylate, contains <=250 ppm monomethyl ether hydroquinone as inhibitor, 97%; Hema-ema; Hydroxyethyl methacrylate-ethyl methacrylate; 26335-61-5; EMA HEMA; Hydroxyethylmethacrylate-ethylmethacrylate copolymer; SCHEMBL5534844; CTK4F7688; DTXSID70180949; 2-Propenoic acid, 2-methyl-, ethyl ester, polymer with 2-hydroxyethyl 2-methyl-2-propenoate; Hydroxyethylmethacrylate; 2-HYDROXYETHYL METHACRYLATE; hidroksietilmetakrilat; (Hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester; Methacrylic acid, 2-hydroxyethyl ester; β-Hydroxyethyl methacrylate; Ethylene glycol methacrylate; Ethylene glycol monomethacrylate; Glycol methacrylate; Glycol monomethacrylate; Hydroxyethyl methacrylate; Monomer MG-1; 2-(Methacryloyloxy)ethanol; Mhoromer; 2-Methyl-2-propenoic acid, 2-hydroxyethyl ester; Bisomer HEMA; GMA; HEMA; 1,2-Ethanediol, mono(2-methyl)-2-propenyl; NSC 24180; 1,2-Ethanediol, mono(2-methyl)-2-propenoate; 868-77-9; Glycol methacrylate; glikol metakrilat; Hydroxyethyl methacrylate; hidroksimetil metakrilat; Glycol monomethacrylate; glikol monometakrilat; hikroksietil metakrilat; metakrilate; iki hidroksimetil metakrilat; hidroksi etil metakrilat; methakrilat; hidroksi metil metakrilat; Ethylene glycol methacrylate; HEMA; 2-(Methacryloyloxy)ethanol; etilen glikol metrakrilat; akrilat; akrilate; 2-Hydroxyethylmethacrylate; Mhoromer; Ethylene glycol monomethacrylate; Monomer MG-1; 2-hydroxyethyl 2-methylprop-2-enoate; Methacrylic acid, 2-hydroxyethyl ester; hidroksietil ester; hidroksi etil ester; (hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester PHEMA, h e m a; beta-Hydroxyethyl methacrylate; beta hidroksi metakrilat; NSC 24180; 2-Hydroxyethyl 2-methylacrylate; UNII-6E1I4IV47V; PEG-5 methacrylate; CCRIS 6879; CHEBI:34288; Ethylene glycol, monomethacrylate; HSDB 5442; PEG-MA; POLYHYDROXYETHYL METHACRYLATE; EINECS 212-782-2; BRN 1071583; Monomethacrylic ether of ethylene glycol; metakrilik asit; 6E1I4IV47V; polyethylene glycol methacrylate; .beta.-Hydroxyethyl methacrylate; 1,2-Ethanediol mono(2-methyl)-2-propenoate; MFCD00002863; 12676-48-1; methacryloyloxyethyl alcohol; Poly-hema; poli hema; Bisomer HEMA; bizomer hema; 2-Hydroxyethyl methacrylate, 97%, stabilized; Hydroxymethacrylate gel; hidroksi metakrilat jel; Polyglycol methacrylate; Glycol methacrylate gel; Poly(hydroxyethyl methacrylate); PEG-8 methacrylate; hydroxyethylmethacrylate; HYDROXYETHYL METACRYLATE; hydroxyehtyl methacrylate; hydroxylethyl methacrylate; 2-hydroxyetyl methacrylate; DSSTox_CID_2128; HEMA (Hidroksietil Metakrilat, Hydroxyethyl Metacrylate) synonyms: 2-HYDROXYETHYL METHACRYLATE; (Hydroxyethyl)methacrylate; 2-Propenoic acid, 2-methyl-, 2-hydroxyethyl ester; Methacrylic acid, 2-hydroxyethyl ester; β-Hydroxyethyl methacrylate; Ethylene glycol methacrylate; Ethylene glycol monomethacrylate; Glycol methacrylate; Glycol monomethacrylate; Hydroxyethyl methacrylate; Monomer MG-1; 2-(Methacryloyloxy)ethanol; Mhoromer; 2-Methyl-2-propenoic acid, 2-hydroxyethyl ester; Bisomer HEMA (Hidroksietil Metakrilat, Hydroxyethyl Metacrylate); GMA; HEMA (Hidroksietil Metakrilat, Hydroxyethyl Metacrylate); 1,2-Ethanediol, mono(2-methyl)-2-propenyl; NSC 24180; 1,2-Ethanediol, mono(2-methyl)-2-propenoate; 868-77-9; Glycol methacrylate; glikol metakrilat; Hydroxyethyl methacrylate; hidroksimetil metakrilat; Glycol monomethacrylate; glikol monometakrilat; hikroksietil metakrilat; metakrilate; iki hidroksimetil metakrilat; hidroksi etil metakrilat; methakrilat; hidroksi metil metakrilat; Ethylene glycol methacrylate; HEMA (Hidroksietil Metakrilat, Hydroxyethyl Metacrylate); 2-(Methacryloyloxy)ethanol; etilen glikol metrakrilat; akrilat; akrilate

HEMA (Hydroxyethyl Metacrylate)

Molar Mass of HEMA (Hydroxyethyl Metacrylate): 130.14 g/mol
Hill Formula: C₆H₁₀O₃
Chemical Formula: CH₂=C(CH₃)COOCH₂CH₂OH
CAS No: 868-77-9
EC Number: 212-782-2
Hydroxyethylmethacrylate or HEMA (Hydroxyethyl Metacrylate) is the organic compound with the formula H2C=C(CH3)CO2CH2CH2OH. It is a colorless viscous liquid that readily polymerizes. HEMA (Hydroxyethyl Metacrylate) is a monomer that is used to make various polymers.

Applications of HEMA (Hydroxyethyl Metacrylate)
Polyhydroxyethylmethacrylate is hydrophobic; however, when the polymer is subjected to water it will swell due to the molecule's hydrophilic pendant group. Depending on the physical and chemical structure of the polymer, it is capable of absorbing from 10 to 600% water relative to the dry weight. Because of this property, it was one of the first materials to be successfully used in the manufacture of soft contact lenses[3]

When treated with polyisocyanates, poly(HEMA (Hydroxyethyl Metacrylate)) makes a crosslinked polymer, an acrylic resin, that is a useful component in some paints.
Synthetic Biomaterials for Regenerative Medicine Applications
Satyavrata Samavedi, ... Aaron S. Goldstein, in Regenerative Medicine Applications in Organ Transplantation, 2014

7.5.2 Poly(2-hydroxyethylmethacrylate)
7.5.2.1 Properties of HEMA (Hydroxyethyl Metacrylate)
Poly(2-hydroxyethylmethacrylate) (pHEMA (Hydroxyethyl Metacrylate)) is an inert, water-stable, nondegradable hydrogel [180] with high transparency. The physical properties of pHEMA (Hydroxyethyl Metacrylate) (e.g., swelling, stiffness, rheology) can be tuned by varying cross-linking density, incorporating different chemistries through copolymerization, and introducing mesoscopic pores. Specifically, a reduction in cross-linking density results in a softer, more malleable hydrogel [157] that may be better suited for soft tissue regeneration. Moreover, copolymerization with acetic acid, methylmethacrylate, or dextran can adjust the permanence, hydrophilicity, and cellular adhesion in vivo[158,181,182]. Finally, the introduction of mesoscopic porogens can facilitate vascular ingrowth, improve cellular attachment, and overcome limited permeability [159,183]. Although pHEMA (Hydroxyethyl Metacrylate) is considered nondegradable (which makes it ideally suited for long-term applications in vivo), degradable pHEMA (Hydroxyethyl Metacrylate) copolymers have been fabricated by the integration of enzymatically susceptible monomers (e.g., dextran) or cross-linking agents [158]. These degradable materials show promise for controlled release of pharmaceuticals and proteins [158,160,184].

7.5.2.2 Applications of HEMA (Hydroxyethyl Metacrylate)
Due to its excellent optical properties, pHEMA (Hydroxyethyl Metacrylate) has primarily been used in ophthalmic applications [157] under the generic names etafilcon A and vifilcon A. In addition, it has been examined for controlled release of proteins and drugs [158,161], engineering of cardiac tissue [159], axonal regeneration in spinal cord injury [160], and replacement of intervertebral discs [162]. However, two limitations of pHEMA (Hydroxyethyl Metacrylate) are its propensity for calcification and the toxicity of the 2-hydroxyethylmethacrylate monomers. Phase I testing of pHEMA (Hydroxyethyl Metacrylate) for corneal prostheses (keratoprosthesis) revealed calcium salt deposition within 2.5 years after implantation [180,181]. At the same time, residual HEMA (Hydroxyethyl Metacrylate) monomer can compromise the mechanical properties of the hydrogel, and leach into surrounding tissue with toxic effects
Because 2-hydroxyethyl methacrylate is very important in macromolecular chemistry. This paper reviews the main properties of the polymers or copolymers prepared from it by summarizing the information published in articles or patients. The following plan is adopted: Preparation and purification of 2-hydroxyethyl methacrylate Polymerization and copolymerization of 2-hydroxyethyl methacrylate and physical properties Chemical modifications of monomer Chemical modifications of poly-2-hydroxyethyl methacrylate and related copolymers Grafting reactions of polymer or copolymer Applications in biomedical fields The following abbreviations will be used: HEMA (Hydroxyethyl Metacrylate) for 2-hydroxyethyl methacrylate (rather than GMA, which is chiefly employed in medical journals) and PHEMA (Hydroxyethyl Metacrylate) for the corresponding polymers. EGDMA will be used for ethylene glycol dimethacrylate, an impurity synthesized in the preparation of monomer.
2-Hydroxyethyl methacrylate (HEMA (Hydroxyethyl Metacrylate)) is perhaps the most widely studied and used neutral hydrophilic monomer. The monomer is soluble, its homopolymer is water-insoluble but plasticized and swollen in water. This monomer is the basis for many hydrogel products such as soft contact lenses, as well as polymer binders for controlled drug release, absorbents for body fluids and lubricious coatings. As a co-monomer with other ester monomers, HEMA (Hydroxyethyl Metacrylate) can be used to control hydrophobicity or introduce reactive sites.
2-Hydroxyethyl methacrylate (HEMA (Hydroxyethyl Metacrylate)) is perhaps the most widely studied and used neutral hydrophilic monomer. The monomer is soluble, its homopolymer is water-insoluble but plasticized and swollen in water. This monomer is the basis for many hydrogel products such as soft contact lenses, as well as polymer binders for controlled drug release, absorbents for body fluids and lubricious coatings. As a co-monomer with other ester monomers, HEMA (Hydroxyethyl Metacrylate) can be used to control hydrophobicity or introduce reactive sites.

glycol methacrylate
Technical grade: Purity %=min. 97; Acid Content %=max 1.5;
EGDMA content %=max 0.2; Color=50

Because 2-hydroxyethyl methacrylate is very important in macromolecular chemistry. This paper reviews the main properties of the polymers or copolymers prepared from it by summarizing the information published in articles or patients. The following plan is adopted: Preparation and purification of 2-hydroxyethyl methacrylate Polymerization and copolymerization of 2-hydroxyethyl methacrylate and physical properties Chemical modifications of monomer Chemical modifications of poly-2-hydroxyethyl methacrylate and related copolymers Grafting reactions of polymer or copolymer Applications in biomedical fields The following abbreviations will be used: HEMA (Hydroxyethyl Metacrylate) for 2-hydroxyethyl methacrylate (rather than GMA, which is chiefly employed in medical journals) and PHEMA (Hydroxyethyl Metacrylate) for the corresponding polymers. EGDMA will be used for ethylene glycol dimethacrylate, an impurity synthesized in the preparation of monomer.

method is the reaction of ethylene oxide and methacrylic acid (Scheme 2) [8-lo]. The HEMA (Hydroxyethyl Metacrylate) prepared by these two methods contains impurities in various percentages: e.g., methacrylic acid results from a hydrolysis reaction of HEMA (Hydroxyethyl Metacrylate) and EGDMA coming from esterification between methacrylic acid or HEMA (Hydroxyethyl Metacrylate) and ethylene glycol. Since HEMA (Hydroxyethyl Metacrylate) is a commercial product, it seems more useful to summarize the various purification procedures rather than the numerous works about industrial preparations because the commercial product contains EGDMA and methacrylic acid in monomer proportions. The main procedures use the solubility of HEMA (Hydroxyethyl Metacrylate) in water or diethyl ether and its nonsolubility in hexane. EGDMA is soluble in hexane. Therefore, HEMA (Hydroxyethyl Metacrylate) is dissolved in four volumes of water and EGDMA is extracted with hexane. Then the aqueous solution of HEMA (Hydroxyethyl Metacrylate) is salted to complex methacrylic acid. HEMA (Hydroxyethyl Metacrylate) is extracted with diethyl ether, the solution is dried, and HEMA (Hydroxyethyl Metacrylate) is distilled under vacuum (11-141. The elimination of methacrylic acid can also be carried out by soaking technical HEMA (Hydroxyethyl Metacrylate) with anhydrous sodium carbonate [15] and extracting EGDMA with hexane. Then HEMA (Hydroxyethyl Metacrylate) is extracted with diethyl ether and distilled as previously described. The use of ion-exchange resins (Amberlyst A 21) is a simple method of elimination of methacrylic acid [ 16-18] but the yield is rather poor. N,N'-Dicyclohexylcarbodiimide has also been used for the elimination of methacrylic acid [19], but variations in the quality of the reagent often outweigh the value of the method. Lastly, extraction of EGDMA with hexane followed by the washing of a dilute solution of HEMA (Hydroxyethyl Metacrylate) in water with sodium hydroxyde or sodium bicarbonate and the extraction of HEMA (Hydroxyethyl Metacrylate) with chloroform gives, after drying and evaporation of chloroform, a product of high purity for the preparation of resins for optical microscopy [20, 211. The purity of the monomer can be checked by using vapor-phase chromatography [22,24], liquid chromatography [15], or thin layer chromatography [25]. Detailed distillation procedures to avoid polymerization of HEMA (Hydroxyethyl Metacrylate) have been described.

Polymerization As for the majority of methacrylic derivatives, HEMA (Hydroxyethyl Metacrylate) can be polymerized by radical initiators or by various methods (y-rays, UV, and plasma). When the monomer is purified (without EGDMA, which is a crosslinking product), a soluble polymer can be synthesized, but when the monomer contains even a low percentage of EGDMA, the prepared copolymers produce swollen gels in water and in many other solvents A summary of the main procedures of polymerization is given in Table 1. Syndiotactic PHEMA (Hydroxyethyl Metacrylate) has been synthesized by UV catalysis at - 40"C, and isotactic PHEMA (Hydroxyethyl Metacrylate) has been prepared through hydrolysis of poly(benzoxyethy1 methacrylate) which had been synthesized from the corresponding polymers with dibutyl lithium cuprate as catalyst [52]. ~41. 3.1.2. Physical Properties of PHEMA (Hydroxyethyl Metacrylate) Because PHEMA (Hydroxyethyl Metacrylate) has numerous applications in biomedicine, its physical properties have been widely studied. 3.1.2.1. Studies of Diffusion. The permeability of PHEMA (Hydroxyethyl Metacrylate), used as a membrane for oxygen, has been compared to other macromolecules [53]. The diffusion of water through hydrogels of PHEMA (Hydroxyethyl Metacrylate), crosslinked with low percentages of EGDMA, has also been studied [54, 571. The influence of the degree of crosslinking [58, 601, the diffusion laws, the measurement of the equilibrium constant with water, and a structural study of swollen gels were recently published [61]. 3.1.2.2. Mechanical and Viscoelastic Properties. These properties were summarized in two previous reviews [62, 631. Composites with crosslinked PHEMA (Hydroxyethyl Metacrylate) have good elastic properties [64,65]. The influence of aqueous solutions of sodium chloride on the elasticity of PHEMA (Hydroxyethyl Metacrylate) has also been studied in relation to its use for optical lenses [66]. Viscometry, Thermal, and Dielectric Properties, and NMR Characterizations. Because the Mark-Houwink parameters in many solvents are well known, the molecular weights of PHEMA (Hydroxyethyl Metacrylate) can be measured by viscosity.

Lastly, in order to use the PHEMA (Hydroxyethyl Metacrylate) in the biomedical field, the purification of polymer gel has been described [80]. 3.1.3. Copolymerization Reactions of HEMA (Hydroxyethyl Metacrylate) Copolymerization reactions of this monomer have been studied for its fundamental properties (determination of reactivity ratios, AlfreyPrice parameters) [81, 821 and its applications in various fields. The main results are given in Table 2. Some examples of block copolymerization with styrene [104, 1051, 2- phenyl-1,2,3-dioxaphospholane [ 1061, and with macromonomers [ 1071 of polyamine [lo81 or polyurethane [lo91 can be cited. Lastly, fundamental studies on the copolymerization of methyl methacrylate with HEMA (Hydroxyethyl Metacrylate) [110] and the determination of the composition of its copolymer have been made, and a model of the copolymerization of HEMA (Hydroxyethyl Metacrylate) and EDGMA was recently published [ 11 11. 4. CHEMICAL MODIFICATIONS OF MONOMER Because HEMA (Hydroxyethyl Metacrylate) has a primary alcohol function a great number of nucleophilic reactions have been achieved and generally the modified monomer can be polymerized. A summary of the main chemical modifications is given in Table 3. 5. CHEMICAL MODIFICATIONS OF PHEMA (Hydroxyethyl Metacrylate) AND RELATED COPOLYMERS A relatively low number of chemical modifications of PHEMA (Hydroxyethyl Metacrylate) have been registered because chemical modifications of the corresponding monomer as well as its polymerization are easy to achieve. The listing of these reactions is given in Table 4. 6. GRAFTING REACTIONS OF POLYMER AND COPOLYMER By using various techniques, the grafting of PHEMA (Hydroxyethyl Metacrylate) and copolymers prepared with HEMA (Hydroxyethyl Metacrylate) as a comonomer has been carried out with natural polymers such as cellulose [148], dextran [149], and starch.

APPLICATIONS IN BIOMEDICAL FIELDS Because HEMA (Hydroxyethyl Metacrylate) can be easily polymerized, possesses a hydrophilic pendant group, and can form hydrogels, an increasing number of applications have been found in various biomedical fields. Although, as previously mentioned, a complete listing of the literature references appears impossible, we have tried to present the main areas of interest for HEMA (Hydroxyethyl Metacrylate), either when used alone or in combination with other chemical reagents. 7.1. Irritant and Toxic Effects First of all, the low toxicity of the monomer is widely accepted but few reports are available on the (potent) irritant effects of HEMA (Hydroxyethyl Metacrylate). Intradermal injection of crude HEMA (Hydroxyethyl Metacrylate) monomer at low concentrations in saline solution (-1%) was found to induce a very mild irritation in the rat, while higher concentrations (up to 20%) were associated with a pronounced reaction. Similar findings were observed with sodium benzoate (an end product of benzoyl peroxide degradation used as a polymerization initiator) emphasizing the irritant role of residues [ 1591. PHEMA (Hydroxyethyl Metacrylate) gels implanted into muscles of rats were found to release residual irritant continuously but at a very low rate, thus inducing no cellular reaction [160]. HEMA (Hydroxyethyl Metacrylate) used at 0.01-1% concentrations was found to alter the fine structure of cultured cells with quantitative video microscopy [161]. On the other hand, numerous clinical trials, listed hereafter within a specific organ description, have found minimal irritant reactions. 7.2. Histological Embedding
The use of HEMA (Hydroxyethyl Metacrylate) in histological practice (i.e., the study of living tissues and cells at the microscopic level) was proposed by Rosenberg [162] and Wichterle (1631. The hydrophilic properties of the monomer permit it to be used as a combined dehydrating agent for the tissues and as an embedding medium for electron microscopy. However, blocks Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 2-HYDROXYETHYL METHACRYLATE 15 of pure PHEMA (Hydroxyethyl Metacrylate) appeared difficult to section, and they had poor resistance under an electron beam. The quality of commercially available HEMA (Hydroxyethyl Metacrylate) was reported to vary considerably up to 1965 [164]. Copolymers with n-butyl methacrylate [165] or styrene [166] were also found less satisfactory than the epoxy resins. During the last decade, HEMA (Hydroxyethyl Metacrylate) has found a new interest in light microscopy [167,168]. An extensive review was made by Bennett et al. "1. Briefly, HEMA (Hydroxyethyl Metacrylate) embedding is favored for light microscopy because: 1) The embedding duration is shorter than for classical methods. HEMA (Hydroxyethyl Metacrylate) was used to embed large and very large specimen [169]. 2) Preservation of tissular and cellular structures is far superior to other classical methods [170]. This is due to the adherence of tissue sections onto the microscopic glass slides and because the resin is not removed prior to staining. (3) Sectioning is easier and semithin sections (i.e., 2 to 3 pm in thickness) can be obtained on conventional microtomes with steel or Ralph's glass knives [171]. Furthermore, once cut, the sections spread on water and do not shrink. (4) Numerous staining methods can be performed on PHEMA (Hydroxyethyl Metacrylate) sections. Classical stains (excepted those having a hydro-alcoholic vehicle which makes the section swell) have been reported to work well, sometimes after minor modifications [172]. Enzymological studies can readily be done, and large amounts of enzymes are preserved. Calcified tissue enzymes have been demonstrated on undecalcified sections [ 1731. At the present time, several HEMA (Hydroxyethyl Metacrylate)-based commercial kits are available (Historesin, JB4, . . .) However, the slow hydrolysis of the resin makes it difficult to obtain regular results; the regenerated methacrylic acid appears to combine with basic stains, and small amounts (1.5% or less) impair correct staining by strongly obscuring the background [ 16, 181. Several purification methods specially devoted to histotechnology have been designed [ 16-21]. Copolymerization with dimethylamino ethyl methacrylate was proposed to complex the carboxylic groups of methacrylic acid [174]. HEMA (Hydroxyethyl Metacrylate) alone was repeatedly found to be a poor medium for calcified tissues because the size of the molecule makes it difficult to infiltrate such tissues. Combined with methyl methacrylate (MMA) [ 1751 or various types of aikyl methacrylates or acrylates, HEMA (Hydroxyethyl Metacrylate) was shown to provide suitable embedding media [ 1761. HEMA (Hydroxyethyl Metacrylate) is usually polymerized by a redox reaction (benzoyl peroxide and N,N‘-dimethyl aniline), and the method has been used to embed in the cold, thus preserving enzyme activities [ 169, 1731. Azobisisobutyronitrile has also been proposed [177]. Benzoyl peroxide and UV light were reported to work well, but Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 16 MONTHEARD, CHATZOPOULOS, AND CHAPPARD they induce staining artifacts [178]. Other initiators have also been proposed (barbiturate cyclo compounds, butazolidine [179]). PHEMA (Hydroxyethyl Metacrylate) has been shown to produce better sections when small amounts of crosslinkers are used [171, 1801. We recently showed that HEMA (Hydroxyethyl Metacrylate) embedding is an inhomogeneous mechanism and that it varies according to the volume of monomer to be bulk polymerized [ 1811. 7.3. Dentistry Synthetic apatitic calcium phosphate cements were prepared with a PHEMA (Hydroxyethyl Metacrylate) hydrogel containing tetracalcium phosphate and dicalcium phosphate [182].

PHEMA (Hydroxyethyl Metacrylate) was found to be a highly biocompatible and resorbable material for primary teeth endodontic filling [ 1831. However, due to its hydrophilicity, PHEMA (Hydroxyethyl Metacrylate) appeared more useful in dentistry as a bonding reagent between dentine and other types of restorative resins; varying mixtures of HEMA (Hydroxyethyl Metacrylate) and glutaraldehyde were investigated [ 184, 1851. Other bonding complexes using PHEMA (Hydroxyethyl Metacrylate) have been reported for enamel and dentine [186]. HEMA (Hydroxyethyl Metacrylate) was found to be a suitable vehicle for dentin self-etching primers (such as acidic monomers) [187]. Other clinical trials have been done with an antiseptic (chlorhexidine) entrapped in a HEMA (Hydroxyethyl Metacrylate)/MMA copolymer membrane to develop a controlled release delivery system [188]. However, PHEMA (Hydroxyethyl Metacrylate) was found unsuitable as a permanent soft lining material for covering the oral mucosa in denture-bearing areas [189]. 7.4. Immobilization of Molecules and Cells Immobilization implies the entrapment within a polymeric network of a definite "foreign" compound (i.e., an enzyme, a drug, a cell, . . .), whether it is simply confined or grafted onto the polymeric chains. 7.5. Immobilization of Enzymes Immobilization of several enzymes on solid supports has found a number of applications in biotechnology because enzyme molecules become reusable and side products are not obtained [190]. In order to preserve enzyme activity, radiation-induced polymerization is often reported: Cellulase was found to be well preserved in HEMA (Hydroxyethyl Metacrylate) polymerized by y-radiation (5 x lo5 to 5 x loh rad) at low temperature after salting Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 2-HYDROXYETHYL METHACRYLATE 17 out the monomer [191]. Trypsin was found to bind covalently on a composite material made of an alginate copolymerized with HEMA (Hydroxyethyl Metacrylate) and glycidyl methacrylate. The loss of enzyme activity was only 7% after five successive uses [192]. Glucose oxidase was readily immobilized in PHEMA (Hydroxyethyl Metacrylate) membranes, but the affinity of the enzyme for its substrate (glucose) was substantially decreased [193]. The activity of lipase was decreased when immobilized in PHEMA (Hydroxyethyl Metacrylate) due to the hydrophobic character of the enzyme itself [194]. The location of the enzyme within the hydrogel has been studied. The distribution of fluorescein isothiocyanate-labeled glucoamylase was investigated with fluorescence microscopy. The enzyme was found to be located on the interface between the polymer membrane, the pore structures, and partly in the polymer itself [ 1951. A PHEMA (Hydroxyethyl Metacrylate) and ethylene dimethacrylate copolymer (Separon HEMA (Hydroxyethyl Metacrylate)) was used to study the covalent immobilization of various enzymes. The type and concentrations of added salts were found to modify yields [ 1961. Membranes of PHEMA (Hydroxyethyl Metacrylate) containing glucose oxidase were found to swell in glucose solutions and may be used for glucose monitoring in artificial pancreases [ 1971. 7.6. Immobilization of Cells Several types of microbial cells or yeasts known to have biotechnologically interesting enzymes have been entrapped into PHEMA (Hydroxyethyl Metacrylate) hydrogels (e.g., Streptornyces phaechrornogenes containing glucose isomerase [ 1981 and Mortiella vinacea containing a galactosidase [ 1991). Pancreatic islets enclosed in a PHEMA (Hydroxyethyl Metacrylate) hydrogel were found to synthesize and release insuline in vitro [200]. The biocompatibility of such pancreatic islets was found to be excellent when implanted into animals [201]. Diffusion chambers made of a PHEMA (Hydroxyethyl Metacrylate) hydrogel were successfully used in vivo after immobilization of rabbit embryos; the chamber was implanted in the peritoneal cavity of male mice and early developmental stages were followed [202]. A hydrogel of pure PHEMA (Hydroxyethyl Metacrylate) has no effect on spermatozoid motility, but the copolymer of HEMA (Hydroxyethyl Metacrylate)-methacrylic acid inhibited 100% of spermatozoa after 30 min; the latter might be used as a male contraceptive technique when injected into the vas deferens [203]. Composites of alginate and HEMA (Hydroxyethyl Metacrylate) have been used to prepare microspheres for the microencapsulation of cells [204]. A detailed method for Chinese hamster ovary fibroblast encapsulation was reported [205]. Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 18 MONTHEARD, CHATZOPOULOS, AND CHAPPARD 7.7. Immobilization of Drugs Numerous drugs have been entrapped (or immobilized) in radiationpolymerized HEMA (Hydroxyethyl Metacrylate) in order to produce drug delivery devices, e.g., ergotamine [14], salicylic acid.
The ability of various drugs to diffuse into polymers may be used in various types of biotechnologies such as membrane separation and drug delivery devices. The prediction of drug solubilities in PHEMA (Hydroxyethyl Metacrylate) and other polymers has been studied [209]. Immobilization of chloramphenicol in PHEMA (Hydroxyethyl Metacrylate) hydrogels crosslinked with EGDMA was found to be released upon swelling of the gel in water; the diffusion obeyed Fick's second law [210]. The kinetics of thiamine (vitamin B1) diffusion from previously loaded PHEMA (Hydroxyethyl Metacrylate) beads was studied at 37.5"C in water [211]. Theophyllin release from an amphiphilic composite made of PHEMA (Hydroxyethyl Metacrylate) and polyisobutylene was studied from a kinetic point of view [212]. PHEMA (Hydroxyethyl Metacrylate) membranes are favored as transdermal delivery systems for long-term constant drug delivery [213]. Vidarabine (an antiviral agent) was entrapped to PHEMA (Hydroxyethyl Metacrylate) membranes and used for transdermal patches: the blood-drug concentrations could be predicted and the permeability coefficient of the membranes could be adjusted by controlling hydration [214, 2151. Similar observations were obtained with progesterone [216]. Nitroglycerin was also entrapped in PHEMA (Hydroxyethyl Metacrylate) membranes to provide a transdermal delivery system [217]. Synthetic organ substitutes having the capacity to slowly release hormones have been designed: diffusivity of insulin through PHEMA (Hydroxyethyl Metacrylate) membranes was studied [218]. Because PHEMA (Hydroxyethyl Metacrylate) hydrogels are hardly degraded in vivo, it was found that entrapment of drugs (testosterone) in a blend of PHEMA (Hydroxyethyl Metacrylate)/albumin resulted in a slowly degraded matrix with continuous release of the drug. Testicular prosthesis releasing testosterone have been done [219, 2201. Anticancer drugs have been extensively entrapped in matrices of PHEMA (Hydroxyethyl Metacrylate), thus providing a hard material which can be implanted into the tumor where it delivers higher amounts of drug in situ [221]. 5- Fluorouracil was embedded in HEMA (Hydroxyethyl Metacrylate)/bisglycol acrylate copolymer in 3 mm diameter beads which could be implanted subcutaneously [222]. Methotrexate and 3'3'-dibromoaminopterin were absorbed on PHEMA (Hydroxyethyl Metacrylate) and used as local intratumoral implants in Gardner's lymphosarcoma of the C3H mouse [223]. The effect of crosslinking on the swelling of PHEMA (Hydroxyethyl Metacrylate) gels (and the drug diffusion coefficient through these gels) has been explored [224]. Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 PHYDROXYETHYL METHACRYLATE 19 Finally, various substances have been immobilized in PHEMA (Hydroxyethyl Metacrylate) in order to prepare diagnostic tools. An antiserum-raised methotrexate was entrapped in PHEMA (Hydroxyethyl Metacrylate) during polymerization. The lyophilized powder was used for radioimmunoassay of this anticancer drug [225]. The entrapment of immunoglobulins has been used for immunochemical studies [226]. The Fc fragment of immunoglobulins has been grafted onto Separon HEMA (Hydroxyethyl Metacrylate) resins after periodate oxidation, thus providing immuno-affinity sorbents for the isolation of proteins [227]. A dye, Cibracron Blue F3GA, was entrapped within the pores of a nylon/ PHEMA (Hydroxyethyl Metacrylate) gel used for protein purification [228]. 7.8. Biocompatibility of HEMA (Hydroxyethyl Metacrylate) Biocompatibility of PHEMA (Hydroxyethyl Metacrylate) has been studied at the cell and tissue levels. Cell cultures on PHEMA (Hydroxyethyl Metacrylate)-coated slides or on PHEMA (Hydroxyethyl Metacrylate) hydrogels are used to investigate the intimate mechanisms of cellular compatibility. Implanting pieces of gel in an animal by a surgical procedure allows the study of the adverse reactions of the whole organisms against the resin. Because implantations in the eye or in direct contact with blood induces specific problems, these two aspects of the biocompatibility will be treated separately below. 7.9. Cell Culture The hydrophilicity of the resin was primarily thought to be favorable for cell culture. Cellular adherence to PHEMA (Hydroxyethyl Metacrylate) has been recognized since 1975 when myoblasts from chicken embryos were cultured on polysiloxane grafted with PHEMA (Hydroxyethyl Metacrylate) [229]. Spreading of cells of hamster kidney was found higher on modified PHEMA (Hydroxyethyl Metacrylate) than on polystyrene due to the hydrophilic properties of the resin [230]. Similar experiments done with endothelial cells of newborn cords have shown that cells first adhere to the hydrophilic substrate, then spread and proliferate [231]. However, pure and unmodified PHEMA (Hydroxyethyl Metacrylate) appears unable to support attachment and growth of mammalian cells [232].

PHEMA (Hydroxyethyl Metacrylate) films of increasing thickness decrease cell adhesiveness on culture flasks and alter cell shape [233]. Leukocyte locomotion is suppressed on PHEMA (Hydroxyethyl Metacrylate)-coated glass plates [234]. When malignant melanoma cells are grown on PHEMA (Hydroxyethyl Metacrylate)-coated culture dishes, they form aggregates of round cells and generate polykaryons [235]. Adrenal tumor cells grown on PHEMA (Hydroxyethyl Metacrylate) show decreased steroidogenesis secondary to altered cell shape Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 20 MONTHEARD, CHATZOPOULOS, AND CHAPPARD caused by the hydrophilicity of the polymer [236]. The time required for rat peritoneal macrophages to adhere to HEMA (Hydroxyethyl Metacrylate)/ethyl methacrylate copolymers was found to be higher than to hydroxystyrene/styrene copolymers due to the high hydrophilicity of the former [237]. Decreasing rates of adhesion of staphylococci on MMAIHEMA (Hydroxyethyl Metacrylate) copolymers parallel the increasing HEMA (Hydroxyethyl Metacrylate) content (i.e., the hydrophilicity) [238]. Simple gels of PHEMA (Hydroxyethyl Metacrylate) do not permit cell spreading. When ionizable groups are entrapped, cell spreading is no longer inhibited; when collagen is added, cell proliferation occurs [239]. Peritoneal macrophage adherence decreases as a function of increased hydrophilicity of the polymer, and cellular adherence on PHEMA (Hydroxyethyl Metacrylate) is favored by absorption of proteins of the extracellular milieu: albumin, fibronectine, and immunoglobulines G favor cellular adherence. On the other hand, fibrinogene, elastine, and plasma copolymerized with PHEMA (Hydroxyethyl Metacrylate) hamper this phenomenon [240]. Alternative modifications of PHEMA (Hydroxyethyl Metacrylate) allowing cell proliferation have been to incorporate methacrylic acid, diethylaminoethyl methacrylate, or by treating the polymer with concentrated sulfuric acid (creating surface carboxylic groups) [241]. 7.10. Implants PHEMA (Hydroxyethyl Metacrylate) is a suitable biomaterial for implantation because of its lack of toxicity and high resistance to degradation [242]. Numerous composite biomaterials based on PHEMA (Hydroxyethyl Metacrylate) and collagen blends have been used [243]. By using various additives, the mechanical properties of PHEMA (Hydroxyethyl Metacrylate) hydrogels can be adjusted to various biomedical applications [244]. HEMA (Hydroxyethyl Metacrylate)/methacrylic acid copolymers were found more biocompatible than PHEMA (Hydroxyethyl Metacrylate) alone which induces a giant cell inflammatory reaction when implanted [245]. When collagen was entrapped in PHEMA (Hydroxyethyl Metacrylate) gels, their composites were found highly biocompatible when implanted subcutaneously in rats [246]. Composites with a low collagen content were found to be better preserved in long-term implantation studies whereas those containing higher amounts of collagen exhibited calcification in the early stages, followed by full biodegradation [247]. Calcification of a synthetic biomaterial implies poor biocompatibility. Although the chemical composition appears important, the macroscopic structure and surface characters of a PHEMA (Hydroxyethyl Metacrylate) implant have been shown to play a key role [248). Extensive calcium accumulation in the mitochondria of cells in close contact with the gels was proposed as the primary mechanism Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 2-HYDROXYETHYL METHACRYLATE 21 of calcification [249]; in addition, hydrogels of HEMA (Hydroxyethyl Metacrylate) and methacrylic acid copolymers were found to pick up large amounts of Ca2+ when exposed to aqueous solutions of calcium [250]. This effect was taken into account when porous sponges of PHEMA (Hydroxyethyl Metacrylate) were compared to demineralized bone for inducing ectopic bone formation [251]. Hydrogels of PHEMA (Hydroxyethyl Metacrylate) have an excellent biocompatibility but present poor mechanical properties. The mechanical and hydration properties of PHEMA (Hydroxyethyl Metacrylate) and other polyhydroxyalkyl methacrylate membranes have been studied [252]. Composites of silicone rubber and fine particles of hydrated PHEMA (Hydroxyethyl Metacrylate) were found to combine both advantages [253]. Radiation grafting of HEMA (Hydroxyethyl Metacrylate) was done on polyurethane films (with good mechanical properties) and found to increase hydrophilicity and tolerance [254]. HEMA (Hydroxyethyl Metacrylate) was grafted on polyether urethane area membranes used for hemodialysis; permeability and blood tolerance were improved but tensile strength was reduced [255]. Hemodialysis membranes of PHEMA (Hydroxyethyl Metacrylate) crosslinked with ethylene dimethacrylate have been prepared [256]. The interaction of urea (the end product of protein catabolism) with PHEMA (Hydroxyethyl Metacrylate) hydrogels revealed that small amounts of methacrylic acid may dramatically increase the swelling properties of the gel [15, 2571. 7.1 1. Prosthetic Vascular Implants and Blood Compatibility A very interesting property of PHEMA (Hydroxyethyl Metacrylate)-based hydrogels is their high hemocompatibility. In the presence of blood, thrombus formation is delayed. Because blood is a complex milieu, in this paragraph we consider all the relationships of PHEMA (Hydroxyethyl Metacrylate) with blood cells, endothelial cells (i.e., the inner cells of the blood vessels), orland blood components. Due to the hydrophilicity of PHEMA (Hydroxyethyl Metacrylate), films of styrene-butadiene-styrene had a better blood compatibility when grafted with PHEMA (Hydroxyethyl Metacrylate) [258]. Copolymers of HEMA (Hydroxyethyl Metacrylate)/styrene or HEMA (Hydroxyethyl Metacrylate)/dimethyl siloxane suppress platelet adhesion and aggregation (and thus reduce thrombus formation) by the creation of hydrophilic/hydrophobic microdomains [259]. Similar findings were obtained with HEMA (Hydroxyethyl Metacrylate)/polyethylene oxide and HEMA (Hydroxyethyl Metacrylate)/ polypropylene oxide copolymers [260]. A HEMA (Hydroxyethyl Metacrylate)-polyamine copolymer was found to induce no blood platelet adherence or activation. Also, this copolymer was used to separate T from B lymphocytes subpopulations via its hydrophilic-hydrophobic microdomain composition [261]. Vascular tubes of polyethylene blended with 14% PHEMA (Hydroxyethyl Metacrylate) have a very low thrombogeneity due to hydrophilization of the plastic [262].
Radiation grafting of HEMA (Hydroxyethyl Metacrylate) and N-vinyl pyrrolidone on silicone rubber was used to improve the hydrophilicity of artery-to-vein shunts and thus to reduce thrombus formation [263]. A highly antithrombogenic polymer was prepared by immobilizing the fibrinolytic enzyme urokinase in a PHEMA (Hydroxyethyl Metacrylate) hydrogel [ 2641. Another important aspect of blood compatibility is the power of a biomaterial to activate the complement system. It is a complex system of plasma proteins activated in cascade and involved in the inflammation process. Intraocular lenses made of PHEMA (Hydroxyethyl Metacrylate) were found ineffective in vifro to activate the serum complement system (C3a, C4a, C5a) [265]. HEMA (Hydroxyethyl Metacrylate)-grafted polyethylene tubes were not found to inactivate the complement [266]. On the other hand, copolymers of HEMA (Hydroxyethyl Metacrylate)/ethyl methacrylate were reported to activate the complement when the polymer contained 60% or more HEMA (Hydroxyethyl Metacrylate) [267). Low density lipoprotein adsorption on PHEMA (Hydroxyethyl Metacrylate) was found to be low due to the hydrophilicity of the resin [268]. Particles of PHEMA (Hydroxyethyl Metacrylate) were used to study the phagocytic processes of macrophages and neutrophils [ 269, 2701. The hemocompatibility of PHEMA (Hydroxyethyl Metacrylate) has led to the development of a medical method used to remove endo or exo toxins from blood. Hemoperfusion takes advantage of activated charcoal to bind such toxics (barbiturates, tricyclic antidepressants, . . .) [243]. Activated carbon particles have been encapsulated with PHEMA (Hydroxyethyl Metacrylate) for the construction of hemoperfusion columns; heparinized blood is purified by adsorption of irrelevant toxic molecules onto the entrapped charcoal particles and the cleaned blood is then perfused to the patient [271]. Composites of PHEMA (Hydroxyethyl Metacrylate), PEG, and activated carbon were found useful for other blood perfusion applications [272]. Another important application of PHEMA (Hydroxyethyl Metacrylate) is the occlusion of blood vessels in various organs and principally in tumors (which are always hypervascularized). Spherical particles of PHEMA (Hydroxyethyl Metacrylate) of regular shape were produced by suspension polymerization. When injected in a vessel close to the tumor, the small beads act as emboli and obliterate the smaller vessels. Thus tumor vascularization is stopped and endovascular embolization is followed by tumoral cell necrosis and size reduction of the tumor. The swelling in water of PHEMA (Hydroxyethyl Metacrylate) beads makes them suitable to close obliteration of vessels [273]. Detailed procedures have been published for preparing such porous PHEMA (Hydroxyethyl Metacrylate) beads of regular size suitable as artificial thrombi [274]. Beads can be loaded or coupled with Downloaded by [University of Illinois at Urbana-Champaign] at 07:47 13 May 2013 2-HYDROXYETHYL METHACRYLATE 23 an x-ray contrasting agent (iodine) which helps radiographic tracing [ 2431.

Optical Lenses The main application of PHEMA (Hydroxyethyl Metacrylate) hydrogels is the preparation of contact and intraocular lenses used after cataract extraction [275, 2761. Black pigmented PHEMA (Hydroxyethyl Metacrylate) was used to prepare light-occluding lens after opthalmic surgery [277]. Gentamicin-soaked contact lenses made of a 61.4% PHEMA (Hydroxyethyl Metacrylate) hydrogel were found to retain bactericidal concentrations of the antibiotic up to 3 days of eye contact [278]. Diffusion of oxygen through hydrophilic contact lens is necessary to avoid corneal oedema. With PHEMA (Hydroxyethyl Metacrylate) lenses, this is obtained with a 33-pm thickness [279]. Deep corneal stromal opacities were seen in PHEMA (Hydroxyethyl Metacrylate) contact lenses and were related to chronic corneal anoxia [280]. Deposits are sometimes observed within contact lenses. They occur after 12 months of daily lens wear and may be associated with vision decrement (2811. The protein deposits on contact lenses vary according to the copolymer: With HEMA (Hydroxyethyl Metacrylate)Imethacrylic acid copolymers, lenses absorb large amounts of lysosyme, and HEMA (Hydroxyethyl Metacrylate)IMMA copolymer preferentially adsorbs albumin [282]. Contact lenses of copolymers of HEMA (Hydroxyethyl Metacrylate) with methacrylic acid or various silanes were found to adsorb less lysosyme than unsilanized lenses [283]. Deposits of calcium in contact lens made of PHEMA (Hydroxyethyl Metacrylate) have been reported [284]. Intraocular strips of PHEMA (Hydroxyethyl Metacrylate) hydrogels containing small amounts (1.2-1.4%) of methacrylic acid were found to be favorably tolerated in vivo due to the high water and carboxylic group content (2851. PHEMA (Hydroxyethyl Metacrylate) intraocular lens were found to be better tolerated than conventional amino-polyamide-base implants, but the presence of microvilli on corneal cells suggests the release of impurities from the resin [286]. PHEMA (Hydroxyethyl Metacrylate)-based intraocular lenses were found to be well preserved after Nd:YAG laser surgery (2871. Various drugs (chloramphenicol, pilocarpine, dexamethasone, . . .) were found to have a longer washout period when entrapped in intraocular lenses than in the human lens [288]. The clinicobiological results of PHEMA (Hydroxyethyl Metacrylate) intraocular lenses were found to be the most favorable, with 92% of implanted patients recovering visual acuity [289]. In a multicenter and international trial, PHEMA (Hydroxyethyl Metacrylate) intraocular lenses were found to be the most favorable clinically [290].